1. Field of the Invention
This invention in general relates to photography and in particular to a scanning type shutter blade arrangement and a variable focus optical system coupled together such that the optical system focuses for predetermined subject distances as the shutter blade arrangement provides different aperture sizes to facilitate exposure.
2. Description of the Prior Art
Camera exposure control systems employing scanning type shutter arrangements are well-known in the photographic art as is shown in the disclosures of, for example, U.S. Pat. Nos. 3,762,299; 3,972,058; and 4,047,190. Typically, the scanning type shutter comprises a pair of opaque blade elements which are mounted for counter-reciprocating motion with respect to one another. Each blade element has a primary aperture of predetermined size and shape located so that, when the blade elements are in one position, the blade element apertures are misaligned and the camera light path is blocked. When the blade elements are moved from their blocking position, however, the blade element apertures progressively overlap one another and become aligned with the camera optical path to define a varying sized exposure aperture. Displacement of the blade elements is usually effected by a solenoid and spring and/or latch arrangement under the control of suitable electronics.
The blade elements also may be initially arranged so that the camera optical path is fully unblocked to facilitate reflex viewing through the camera taking lens and thereafter the camera optical path can be closed and reopened during an exposure cycle or, alternatively, the blade elements can simply unblock the camera path from a fully blocking arrangement during an exposure cycle.
Under natural lighting conditions, the exposure interval of the scanning type shutter blade arrangement, i.e., the period of time during which the blade element apertures overlap to define the variable exposure aperture, is usually regulated by a scene light integrating arrangement which evaluates scene brightness and commands the solenoid to drive the blade elements to return them to their blocking position after they have begun opening to thereby terminate film exposure.
Scanning type shutter blade arrangements have also been adapted in a variety of ways to operate in conjunction with artificial light sources which are utilized to illuminate a scene when the natural available light is too low for adequate exposure.
One of the ways in which the scanning type shutter blade arrangements has been adapted for flash operation to provide proper exposure control is shown in U.S. Pat. No. 3,750,543. Here, a second solenoid driven arrangement inserts a stop within the locus of travel of the blade elements to arrest their movement to define a flash exposure aperture preselected in correspondence with the state of focus of the camera objective lens. The stop is positioned by a cam arrangement which is coupled to the focusing movement of the camera objective lens. This type of arrangement is referred to as "follow focus" flash exposure control because the size of the exposure aperture is set in accordance with the state of focus of the camera lens and hence the distance by which the subject is separated from the camera.
Camera objective lenses frequently used in the above-noted type of follow focus flash exposure control arrangements are frequently variable focal length lenses of the type which have their focal length continuously changed by manually changing the axial air spacing between their elements. However, focus of this type of lens can also be adjusted automatically through the use of automatic ranging apparatus such as the well-known ultrasonic ranging systems described, for example, in U.S. Pat. No. 4,167,316.
Another type of adjustable optical system known to be used in connection with scanning shutter blade arrangements is described in U.S. Pat. No. 4,167,316. Here, a prime lens and a lens disk comprise the optical system. The lens disk alters the optical power of the prime lens depending on the position of the lens disk, which is automatically controlled by a sonar ranging arrangement. In this manner proper focus of the optical system is achieved for preselected ranges of subject distances.
Other types of known variable focal length optical systems are disclosed in U.S. Pat. Nos. 3,305,294 and 3,583,790. In these disclosures, focal length changes are effected by displacing a pair of specially configured optical refracting plates in opposite directions transverse to their optical axes.
It is a primary object of the present invention to provide a scanning type shutter blade arrangement and a variable focus optical system which cooperate such that the optical system focuses for predetermined subject distances as the shutter blade arrangement provides different sized apertures to facilitate film exposure.
Another object of the present invention is to provide a camera exposure control system in which the motion of a scanning type shutter blade arrangement is utilized to set the focus of a variable focal length optical system of the type wherein focal length changes are effected by lateral displacement of a pair of specially configured optical refracting plates.
Another object of the present invention is to provide a camera flash exposure control system in which an exposure aperture and the focus of a lens are properly set in a synchronous manner for predetermined subject distances.
Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the apparatus possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.